Words named after the Roman god of gateways, who had faces on the front and back of his head. Such words are their own opposites. It’s not a phenomenon limited to English; ‘didh’ is Arabic for the category of words that also mean their opposites. Here are some of the most common.
Dust: When you dust your furniture, you remove dust. But when you dust your face with make up, you add fine powder. Not an order to be confused at home.